And when they are told (since the sign of a believer is believing in whatever God has sent down): "Believe in that which He has sent down (on Muhammad, namely the Qur’an)," they retort: "We believe in only what was sent down on us," and they disbelieve in what is beyond that, though it is the truth, confirming what (of the truth) they already possess. Say (to them, O Messenger): "Why then did you kill the Prophets of God before, if indeed you are believers (loyal to what was sent down on you)?"